Self-Shielded, Integrated-Control Radiosurgery System

ABSTRACT

A self-shielded and computer controlled system for performing non-invasive stereotactic radiosurgery and precision radiotherapy using a linear accelerator mounted within a two degree-of-freedom radiation shield coupled to a three-degree of freedom patient table is provided. The radiation shield can include an axial shield rotatable about an axial axis and an oblique shield independently rotatable about an oblique axis, thereby providing improved range of trajectories of the therapeutic and diagnostic radiation beams. Such shields can be balanced about their respective axes of rotation and about a common support structure to facilitate ease of movement. Such systems can further include an imaging system to accurately deliver radiation to the treatment target and automatically make corrections needed to maintain the anatomical target at the system isocenter. Various subsystems to automate controlled and coordinated movement of the movable shield components and operation of the treatment related subsystems to optimize performance and ensure safety are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 16/123,834 filed Sep. 6, 2018 (Allowed); which claims thebenefit of U.S. Provisional Appln. No. 62/554,876 filed Sep. 6, 2017;and PCT Appln. No. PCT/US2017/054880 filed Oct. 3, 2017; the fulldisclosures which are incorporated herein by reference in their entiretyfor all purposes.

This application is generally related to PCT Application No.PCT/US2017/038256 filed Jun. 20, 2017 entitled “Revolving RadiationCollimator;” U.S. Pat. No. 9,308,395 entitled “Radiation Systems withMinimal or No Shielding Requirements on Building;” U.S. Pat. No.9,314,160 entitled “System and Method for Real-Time Target Validationfor Image-Guided Radiation Therapy;” and U.S. Pat. No. 9,604,077entitled “Visualizing Radiation Therapy Beam in Real-Time in the Contextof Patient's Anatomy;” each of which is incorporated herein by referencein its entirety for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of stereotacticradiosurgery. In particular, the invention relates to self-shieldedradiation treatment systems and methods of treatment.

The high-cost of building radiation-shielded rooms for radiosurgeryequipment has created a need for systems that can be offered at a lowercost. Creating a radiosurgical system that is self-shielded accomplishesthis objective, but there are challenges associated with such systems,including complex coordinated function of numerous subsystems to ensuresafe and effective treatment delivery.

While various self-shielded radiosurgical systems have been proposed,there are considerable challenges encountered in executing such systems,which include the high cost and weight of the shielded components, thedifficulties in positioning shielded components due to theirconsiderable weight, and the considerable cost and size of theassociated supports and driving motors that further add to the size andweight of the overall system. These challenges limit the feasibility ofsuch designs and further limit the range of available trajectories oftreatment. Therefore, there is a need for self-shielded systems havingreduced weight and size, and further need for such systems with improveddexterity and range of movement for a therapeutic radiation beam anddiagnostic imaging. It would be desirable for such systems to beconstructed more simply and cost effectively and to have a compact sizeand reduced footprint so as to fit in a standard sized room withoutrequiring a conventional vault or radiation-shielded room, to allow suchtreatment systems to be more widely available for treatment.

BRIEF SUMMARY OF THE INVENTION

The treatment systems described herein are self-shielded and computercontrolled systems for planning and performing non-invasive stereotacticradiosurgery and precision radiotherapy.

In some aspects, the present invention provides substantial advantagesover conventional self-shielded designs by use of a unique shield designand placement that minimizes the amount and weight of shielding thatprevents potential radiation escape, while fulfilling the objectives ofmaintaining anatomical target at isocenter of system, providing maximalrange of MV and kV beam trajectories via independent axial and obliqueshields, and providing mechanical advantages of symmetrically balancingheavy radiation shield components about a relatively small footprintbase ring for a common support. In various embodiments, providingvariable thickness of shields minimizes weight, and balancing theshields in space enables more precise movement of the shield andtherapeutic radiation beam. In one aspect, the invention provides aself-shielded design with movable shield components providing thebenefits described herein and further providing total encapsulation ofthe patient so as to provide total shielding. In some embodiments, sucha system includes axial and oblique shields, as well as a rotary shelland door that allows for complete encapsulation of the patient and totalshielding.

Such systems can include a therapeutic radiation beam emitter, such as alinear accelerator (LINAC), mounted on a two degree-of-freedom rotatableshield assembly, and an imaging system to accurately deliver radiationto the treatment target (e.g. a brain tumor of the patient). In someembodiments, the system includes three independent degrees of freedomassociated with a patient table, added to the two axis of freedom forthe LINAC to provide a total of five degrees of freedom for positioninga target accurately in the iso-center.

In some embodiments, the system uses radiographic information on apatient anatomy (e.g. skull position) to track the patient movement andcorrects for detected patient movement by adjusting the surgical tableprecisely to locate the target at an isocenter of the rotatable shieldassembly. The treatment system includes various hardware and softwaresystems integrally related in the function of the overall system.Subsystems include: mechanical subsystem, patient table subsystem,integrated control subsystem, LINAC subsystem, treatment planningsubsystem, treatment delivery subsystem, imaging and monitoringsubsystems, control subsystem, safety subsystem. Each of thesesubsystems can include corresponding hardware and software componentswithin an integrated robotic system. It is appreciated that the overallsystem is not required to include all the subsystems described hereinand associated features and can include one or more of the subsystems,modifications of the described subsystems, or any combination thereof.

In a first aspect, the systems and methods described herein areconfigured to maintain an anatomical target at an isocenter of thesystem. In some embodiments, the system includes one or more camerasthat can be used for monitoring of a patient and can also be used todetermine and/or verify an isocenter of the system. Such cameras can beincorporated into the collimator assembly, mounted within a movableshield component or mounted to an adjacent structure above the patienttable. In some embodiments, the collimator includes two such camerasdirected towards the patient. In some embodiments, the system includesat least two or more, often four cameras, mounted in a fixed locationabove a patient table, such that the cameras do not move when theradiation shield components are rotated. In some embodiments, the systemcan include one or more cameras that are independently positionable.

In a second aspect, the systems and methods described herein maintain aself-shielded environment. In some embodiments, the self-shieldedenvironment is maintained by coordinated movement of multiple shieldcomponents, at least a first and second shield component that movablyinterface.

In a third aspect, the systems and methods described herein provide animproved or maximal range of both MV and kV beam trajectories fortreatment and imaging via independent axial and oblique shields. In suchsystems, the kV beam emitter can be mounted in the axial shieldcomponent, while the MV beam emitter is mounted within the obliqueshield component, which is rotatable about an oblique axis transverse tothe axial axis of the axial shield component.

In a fourth aspect, the systems and methods described herein provide amechanical advantage by symmetrically balancing shields. In someembodiments, the multiple shield components are supported by a supportring having relatively small footprint as compared to the overall sizeof the system. In some embodiments, mechanical advantages are providedby symmetrically balancing shields about a common support withrelatively small footprint base, permitting shields to be moved withgreater ease and accuracy. In some embodiments, a base ring acts as thecommon support that facilitates precision and accuracy.

In a fifth aspect, the systems and methods described herein provide avariable thickness of oblique shield to minimize the overall weight ofsystem. Portions of the shield components with less exposure to amegavolt (MV) therapy radiation beam and/or a kilovolt (kV) diagnosticradiation beam can have reduced thickness. Such variable thicknessshielding can be formed by mounting additional sheets of shielding alongthe outside of shield portions with higher radiation exposure or can befabricated by variable thickness castings.

In a sixth aspect, the systems described herein are balanced such thatthe weight of the LINAC shield counterbalances the weight of the beamstop. This balancing provides a mechanical advantages that allows formovement of the LINAC shield with a relatively small, lower torquemotor. For instance, if the Center of Gravity (COG) of the moving partsaround the axial axis was off centered (e.g. 5 mm) creating imbalance,then the maximum value of the oscillating torque induced by gravity tocounter act the imbalance would be the weight of the moving shields×Offcenter COG distance to axis of rotation (e.g. 14000 kg×5e−3 m=700 kg·m)which is beyond what the existing motor nominal rated torque is (e.g.300 kg·m).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an overview of a treatment system in accordance withsome embodiments of the invention;

FIG. 2A shows a side view of the system and interface with a supportingbase ring and patient table in accordance with some embodiments;

FIG. 2B shows a front view of the system with an open patient portal inaccordance with some embodiments;

FIG. 3 schematically illustrates the axes of movement of the mechanicalsubsystem and their relationship to one another in a simplified paradigmin accordance with some embodiments;

FIG. 4 shows a patient table and associated axes of motion in accordancewith some embodiments;

FIG. 5 shows the moveable layers of the patient table and axes of motionalong with a simplified model of the respective axes in accordance withsome embodiments;

FIG. 6 illustrates the integrated control subsystem that monitors andcontrols all hardware and software subsystems in accordance with someembodiments;

FIG. 7 schematically illustrates the movable shield components of aself-shielded system in accordance with some embodiments;

FIG. 8 illustrates a system by which the MV radiation that has passedthrough a patient onto a scintillating sheet is captured by a photodiodearray with the resulting signal processed and stored in accordance withsome embodiments;

FIG. 9 illustrates means for verifying the amount of radiation that haspassed through the patient by capturing the fluorescence from ascintillating sheet using a CCD camera in accordance with someembodiments;

FIG. 10 illustrates a specific embodiment of the general scintillatorwith CCD capture as described in FIG. 9, but here in the form of ahardware unit containing both the scintillating sheet and CCD camerathat is removed and replaced in precise intended position between eachpatient use;

FIG. 11 illustrates tracking methodology framework for sequential viewimaging in accordance with some embodiments;

FIG. 12 illustrates a 6D tracking methodology optimization process flowin accordance with some embodiments;

FIG. 13 schematically illustrates shield assembly motion control usingsequential view in accordance with some embodiments; and

FIG. 14 schematically illustrates first and second positions insequential view imaging in accordance with some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

The present invention pertains to self-shielded radiation treatmentsystem, in particular self-shielded systems having a radiation shielddefined by at least two shield components that are balanced and movablyinterfaced so that the shield assembly rotates about a first axis andone of the shield components rotates about a second axis transverse tothe first axis. Such a configuration allows for diagnostic intensity(kKV) imaging from multiple directions for tracking the patient'sposition by rotation of the shielding assembly and further allows fordelivery of therapeutic radiation from a range of directions byindependent rotation of one shield component along the second axis.Balancing of the shield components about their respective axes ofrotation and about a common support and providing shield components ofvariable thickness substantially reduces the weight of the shielding andmakes coordinated and precise controlled movement feasible. Thisapproach also allows for system and drive assembly of more compact size,so as to fit in a standard sized room without requiring an extensiveshielding vault common to conventional radiation treatment systems. Insome embodiments, this configuration allows the main portion includingthe radiation shield to be about 3 meters or less in height and widthand about 30 tons or less in weight for a 3 MV system. It is understoodthat the size and amount of shield depends on the radiation energycapacity of the system being used and that the concepts herein couldapply to any radiation treatment system. Various aspects can be furtherunderstood by reference to the descriptions and example embodimentsdescribed herein.

I. SYSTEM OVERVIEW

In some embodiments, the radiosurgery system includes the followinghardware subsystems and software: mechanical subsystem, patient tablesubsystem, control subsystem, linear accelerator (LINAC) subsystem,treatment planning subsystem, treatment delivery subsystem, imaging andmonitoring subsystem, safety subsystem, and associated softwarecomponents. It is understood that the integrated control system, safetysubsystem and software components can be incorporated into a singlecontrol unit or subsystem. Alternatively, these subsystems could includemultiple coordinated subsystems or units. Each of these subsystems hascorresponding hardware and software components within an integratedrobotic system. It is appreciated that embodiments could include some orany combination of the components, or variations thereof.

In the embodiments of the treatment systems described herein, at leasttwo forms of radiation are emitted and detected: (1) mega-volt (MV)X-ray radiation, which is of therapeutic intensity (e.g. sufficientradiation dosage delivery to kill tumor cells) and (2) kilo-volt (kV)X-ray radiation, which is of diagnostic intensity, and is used to trackthe position of a target (e.g. the patient's skull or body parts) withinthe apparatus to ensure proper MV beam targeting and delivery. In someembodiments, the MV radiation source is affixed within one movableshield component and the kV radiation source is affixed within the othershield component, the shield components together defining a shieldedtreatment space around the target and being movable so as to allowimaging of the target with the kV radiation source from a multipledirections and treatment of the target from the MV radiation source frommultiple directions.

A. Movable Shielding Components

In one aspect, the radiation shield includes a first shield component oraxial shield that is movable about a first axial axis, typicallyhorizontal, that is movably interfaced with a second shield component oroblique shield that is independently rotatable about a second obliqueaxis that is transverse to the first axis. In some embodiments, thefirst axial shield has a generally vertically oriented proximal openingthrough which the patient table and patient are inserted into thetreatment space and a distal angled opening (e.g. 45 degrees) that ismovably interfaced with the second shield or oblique shield such thatsecond axis intersects the first axis at a 45 degree angle. In someembodiments, the oblique axis is generally semi-spherical in shape andincludes a therapeutic radiation beam emitter and beam stop on oppositesides to allow delivery of a therapeutic radiation beam to the targetfrom a path that encircles the target. Coordinated movement of theshields along the first axial axis and movement of the oblique shieldalong the second oblique axis allows for a substantially continuousrange of the therapeutic beam along a majority of a surface of atreatment sphere with only a small portion of the sphere at the proximaland distal ends being inaccessible.

Typically, the first and second shields are formed of iron or ironalloy, or any suitable shield material. Additional shielding of anysuitable material, same or different, can be mounted to the outside ofeach shield in areas exposed to higher radiation levels. In someembodiments, the treatment radiation source or treatment radiation beamemitter (e.g. LINAC) is affixed within one of the shields, while thediagnostic imaging radiation source is disposed within the other shield.The shield components can further include counterweight mounted so as tobalance each shield component or assembly about their respective axes ofrotation.

B. Mechanical Subsystem

In another aspect, the self-shielded radiation treatment system includesa mechanical subsystem that coordinates movement of the movable shieldcomponents to facilitate imaging and treatment from multiple directions.In some embodiments, the mechanical subsystem includes a two degree offreedom rotary electro-mechanical shield assembly that houses the LINACand imaging subsystems. Its purpose is to move the LINAC so as to directthe high-energy treatment beam generated by the LINAC to point at thesystem isocenter (e.g. where the target or tumor will be located) in aprecise fashion. The two degrees of freedom allows a variety of anglesof approach for the treatment beam to be achieved.

In some embodiments, the system includes a rotary shell attached to themechanical rotatable shield assembly that houses a patient tablesubsystem with a vertical door at the end of the rotary shell that movesup and down. These two mechanisms serve as the patient entry/exit to thesystem.

In various embodiments described herein, the mechanical subsystemincludes:

-   -   1. Two moving radiation shields (e.g. axial shield & oblique        shield) which support the radiation treatment beam generator        components.    -   2. A central main base ring that supports the axial and oblique        shields, typically through a bracket with the two rotation axis        bearing.    -   3. A patient entry assembly that supports patient table and        additional static radiation shield.    -   4. Rotary shell along with a vertical radiation shield that        compose the entrance and exit to the treatment space.

In order to provide a head and neck treatment beam solid angle thatwould exceed steradian, the treatment radiation beam generatorcomponents are integrated on the oblique radiation shield supportedwithin an oblique support bracket with two degrees of freedom. In someembodiments, the system is configured to provide the largest solid anglecoverage. Those degrees of freedom are transverse to each other. In thedescribed embodiments, those degrees of freedom are pure rotationsalong:

-   -   1. An axial axis which is horizontal (i.e., perpendicular to        gravity)    -   2. An oblique axis that is oriented 45 degree with respect to        the axial axis. This 45 degree angle remains constant between        those two axes.

In one aspect, those two axes of motion of the two movable shieldcomponents intersect at the isocenter of the treatment system in whichthe patient tumor is located. In some embodiments, a moving patienttable subsystem can be used to ensure the target remains at theisocenter. In the described embodiments, the therapeutic radiation beamgenerator (i.e. LINAC) is integrated such that the beam aims at theisocenter for any position of the radiation shields. In someembodiments, the two movable shield components are supported by a commonsupport, typically a main base ring. This can be accomplished bybalancing of the two movable shield components about the support, asdescribed further below. Typically, the base ring is of castedconstruction and can be anchored to the ground using structuralanchoring methods. This configuration reduces the footprint of theoverall treatment system. The axial rotation of the radiation shieldscan be accomplished using a large slew ring ball bearing. The outer ringof the slew ring bearing can be mounted to the main base ring. The axialbearing is sized to provide the required stiffness to minimize thedeflection of the bearing due to the applied external forces (i.e.,gravity and magnetic attraction load induced by the linear motor). Theinner ring of the axial bearing is clamped between two rotatingassemblies: the axial radiation shield and the oblique radiationshield-mounting bracket (“treatment bracket”). The axial shield alongwith the treatment bracket revolve together around the axial bearingaxis driven by a linear ring motor that includes a set of linear magnetcrescents mounted at the periphery of oblique shield mounting bracket, alarge cage-like structure that encloses the oblique shield andassociated electronic equipment, and which is visible from the posteriorside of the machine. In order to provide enough torque to rotate theaxial assembly, the system uses two motor coil assemblies that include aset of six coils each. Those two assemblies are located side by side atthe bottom of the system main ring assembly to provide a counter momentto the moment due to the moving assembly gravity load. The axial motionposition, velocity and acceleration is controlled using one ring scalealong with two redundant encoder head sensors. While a particularconfiguration of the axial bearing and motor assemblies are describedhere, it is appreciated that various other configurations and anysuitable motor assemblies can be used to provide rotation of the axialshield and oblique shields along the axial bearing axis in keeping withthe described concepts.

In another aspect, the oblique shield is independently rotatable along asecond axis transverse to the axial bearing axis. In the embodimentsdescribed herein, the oblique shield is mounted on the oblique treatmentbracket through the oblique slewing ball bearing, which has a rotationaxis oriented at 45 degrees with respect to the axial bearing axis. Theoblique slew ring ball bearing is sized to provide a required stiffnessto minimize the deflection of the bearing due to the external forcesthat include the gravity and the magnetic attraction load induced by thelinear motor. In some embodiments, the treatment bracket is one part onwhich both axis bearing lodgings are machined, which avoids stackup oftolerances if using more than one bracket and ensures optimal accuracy.The radiation treatment beam generator components are integrated on theoblique radiation shield such that the treatment beam generator can berotated entirely around the target. In order to provide enough torque torotate the oblique shield assembly around the oblique axis, the rotatingshield utilizes two identical motor coil assemblies. Typically, eachmotor coil assembly includes a set of six motor coils. In thisembodiment, oblique shield assembly and the motor coil assemblies aremounted symmetrically in order to vanish the moment due to thecoil/magnet attraction force. This attraction force induces a constantcompressive axial load for the bearing, which is beneficial. In someembodiments, the oblique motion position, velocity and acceleration canbe controlled using one ring scale along with two redundant encoder headsensors. It is appreciated that various other configurations can beused.

In yet another aspect, the treatment system can include a patient entryassembly to facilitate entry of the patient into the shielded treatmentspace defined by the axial and oblique shields. Typically, the patiententry assembly remains static with respect to the rotating axial andoblique radiation shields. In the embodiments described herein, thepatient entry assembly is mounted to the main base ring and includes aradiation shield block as shown in the accompanying figures, a mount forthe patient table, and a rotary shell that serves as a radiation shieldrolling door for the self-shielded capsule system. The rotary shellrotates around the patient table mount by means of a geared slewing ballbearing mounted to the patient entry bracket. The geared bearing can berotated using a pinion driven by a geared electrical motor assembly. Thegeared motor is equipped with a brake that is activated in theloss/absence of electrical power to the system to maintain the rotaryshell in its position. A radiation-shielded vertical door assembly movesvertically to open/close the patient entry of the rotary shell. Thisradiation shield vertical door moves up and down using an actuator. Insome embodiments, the door system is configured such that in the case ofa power loss, the door can be moved down and the patient entry openedwithout power to allow the patient to be removed. For example, the doorcould be opened without power in a controlled manner by manually openinga pressure relief valve, releasing the energy induced by the largevertical gravity load.

In still another aspect, a collimator assembly can be mounted to theLINAC subsystem. An example of collimator assemblies suitable forincorporation into the treatment systems are detailed further in PCTApplication No. PCT/US2017/038256. In such embodiments, the collimatorassembly is spherical/cylindrical and is centered on the LINAC radiationbeam axis. This mechanical axis intersects at the isocenter. Typically,the collimator assembly provides a selectable set of differentcollimator sizes. To achieve this later, those different collimatorsizes can be designed into a revolver. To select the differentcollimator size, the revolver rotates via a harmonic drive (e.g.,geared) electrical motor around an axis perpendicular to the LINACradiation beam axis. This geared motor can be integrated onto the mainhousing, for example, as shown in the accompanying figures. A set of tworedundant rotation encoder head sensors along with a scale can bemounted to the revolver to provide the position control feedback of therevolver to align each collimator size with the LINAC beam axis. In someembodiments, an additional “collimator size” sensor can be used todetermines the proper position/alignment of each collimator size. Thecollimator assembly can be mounted onto the oblique shield, aligned withthe beam axis intersecting the isocenter. Across from this collimatorassembly, a radiation beam stop can be mounted. More shielding can beintegrated around the LINAC to shield the backward scattering radiationfrom the LINAC target. The collimator and the radiation beam stop can beconstructed of any suitable material, although typically, they areformed of tungsten or a tungsten alloy, which allow for a collimator andbeam stop of reduced size for incorporation into the described treatmentsystems.

C. Patient Table Subsystem

In some embodiments, the treatment system includes a movable patientsupport table that is sufficiently movable along multiple axes to allowat least the portion of the patient having the target to be positionedwithin the treatment space defined by the movable shield components. Inthe embodiments described herein, the patient table includes athree-axis mechanism that serves at least two objectives—first, toprovide a bed support on which the patient can lie down comfortablyduring treatment, and second, to accurately maintain position, in threedimensions, of a desired point in the head and neck region at theisocenter, where radiation will be delivered. To accomplish theseobjectives, the patient table can be defined by multiple components thatallow for movement of the patient along multiple axes. In someembodiments, the patient table has at least four sub-sections—lowercart, upper cart, pitch plate and patient bed. The lower cart has thefunction of moving the patient between treatment and extractionpositions. In order to set up the patient for treatment, patient tableextends in a linear rolling fashion, from the shield assembly to theoutside of the patient portal. The upper cart, pitch plate and patientbed together provide the motion needed to accurately position a point inthe head and neck at the isocenter. The upper cart houses the controlcomponents for the patient table. The lower cart, upper cart and patientbed are actuated by linear motors, while the pitch plate is actuated bya rotary motor with a lead screw arrangement. A head support portion ofthe patient table can include facets with which to secure commerciallyavailable radiation face masks, and the patient bed can further includea restraining strap to prevent patient body from significant movementduring delivery. In some embodiments, the head portion can further beconfigured to pitch the patient's head to further increase the availabletreatment range of the LINAC. It is appreciated that the treatmentsystem can utilize a multi-axis patient table without the movable headportion as well.

In some embodiments, the patient table has at least fivesub-sections—table base, lower cart, upper cart, pitch plate and patientbed. The table base provides a fixed support for the patient table. Thetable base acts as the interface between the patient table and themechanical subsystem, that is, the patient table can be attached to themechanical system using the table base. The table base can also provideadditional shielding. The lower cart performs linear motion (Y1 axis)and serves the function of moving the patient between treatment andextraction positions. The lower cart can be driven by any suitablemotor. In some embodiments, the lower cart is driven by a linear motorusing direct drive with no transmission. Such a configuration avoids anypower loss that happens in case of a mechanical transmission like a geartrain. Direct drive is also more responsive. In addition, thisconfiguration is back-drivable which can be an important safety feature.In case of power failure, the lower cart can be pulled out manually dueto its back-drivability. The upper cart performs linear motion (Y2axis), which along with the pitch plate and patient bed, provides themotion needed to accurately position a point in the head and neck regionat the isocenter. The upper cart can be driven by any suitable motor,for example, a linear motor having the advantages as discussed above.The pitch plate can tilt up and down (pitch axis) and, along with theupper cart and patient bed, provide the motion needed to accuratelyposition a point in the head and neck region at the isocenter. In someembodiments, the pitch plate is tilted up and down using a lead screwdriven by a rotary motor. Such a configuration is advantageous since thelead screw is not back-drivable and hence will hold its position duringan accidental power loss. The patient bed can perform an arced side toside rotation (yaw axis) motion driven by any suitable motor. In someembodiments, the yaw rotation is directly driven by a curved linearmotor, which, along with the upper cart and pitch plate, provides themotion needed to accurately position a point in the head and neck regionat the isocenter. Such a configuration is back-drivable as well. From atargeting perspective, the described patient table configurations serveto locate a spatial point {x,y,z} within the patient, at the isocenter(three degrees of freedom provided by the three axes).

In some embodiments, the patient table includes one primary and oneredundant encoder per axis. The link between system computer and motioncontroller can be directly wired or Ethernet. The link between motioncontroller and motor drives can be directly wired or EtherCAT. Motordrives, motors, and encoders are typically located in patient tableassembly.

In another aspect, the treatment planning subsystem is configured to becompatible with the patient table subsystem at the reference frame levelin the world coordinate system. The treatment delivery subsystemaccounts for any possible changes to the patient setup before treatmentis delivered by moving the patient with the patient table so that theanatomic target area is at the physical isocenter of the system, andthis function is continued throughout treatment to compensate for anypatient movement detected by the imaging subsystem.

D. Integrated Control Subsystem

In yet another aspect, the system can include a motion control subsystemthat collectively works to coordinate device position sensor input withthe various motors on the mechanical subsystem and patient tablesubsystem to move the various components of the mechanical subsystem andpatient table to ensure that each radiation beam is properly aimed atthe target within the patient's body, and at assigned trajectories tothe same at the proper times. This ensures that radiation goes only tothe anatomical target. This also enables shielded patient port to beclosed when necessary and open when necessary. These objectives can beachieved by interactively networking the mechanical subsystem, LINACsubsystem, treatment planning subsystem, treatment delivery subsystem,imaging and monitoring subsystem, patient table subsystem, and controland safety subsystem.

Communications between the computer, sensors and actuators can beimplemented by any suitable means, for example using an EtherCATrealtime network (e.g., Beckhoff, Lenze, Sanyo-Denki, ACS) to monitorperipheral sensors and devices and control systems and actuators from amain computer system.

E. LINAC Subsystem

In still another aspect, the system includes a LINAC subsystem thatproduces the treatment beam. Typically, the LINAC subsystem is affixedwithin the second movable shield component (e.g. oblique shieldcomponent) such that movement of the shield component rotates the LINACentirely about the target. The system can be configured to generate acharged particle treatment beam or a photon treatment beam. In someembodiments, the system uses a LINAC to produce a treatment beam with anominal energy of 1 to 5 MeV, preferably 2 to 4 MeV, more preferably 3MeV for a dose rate within a range of 1400 to 1600 cGy/min. In someembodiments, the systems is configured to produce a treatment beam withan energy within a range of 2-3 MV for a dose rate within a range from1000 to 2000 cGy/min. In one aspect, the treatment beam is collimated toproduce one a suitable treatment beam. In some embodiments, the LINACsubsystem is configured to produce a range of differing field sizes, forexample field sizes within a range of 4 to 50 mm. In the embodimentshown, the LINAC subsystem includes eight available field sizes, such asdiameters of 4 mm, 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15 mm, 20 mm and 25 mmat the Source to Axis distance (SAD) of, for example 450 mm. It isappreciated that the LINAC subsystem could be configured to provide acollimated beam at various other diameters as needed for a particulartherapy or target size. Each of the field sizes may be circular andsymmetric, or may be square, rectangular, or any other shape desired. Insome embodiments, the LINAC comes with a variety of safety interlockswhich are integrated in to the control and safety subsystem.

The LINAC subsystem can include any suitable components needed todeliver a given radiation therapy to the target from multipledirections. In the embodiment described herein, the LINAC subsystemincludes the LINAC, motorized secondary collimators, magnetron, solidstate modulator, gun drive power supply, RF waveguide, dosimeter board,automatic frequency control (AFC) board, and LINAC control board. Insome embodiments, the LINAC is configured such that the single photonbeam energy is in the range of 3 MV. In some such embodiments, the depthdose=40±2% for 2.5 cm circular field size at 45 cm Source to SurfaceDistance (SSD) with an ionization ratio of d₂₀₀/d₁₀₀=0.5. In other suchembodiments, the depth dose maximum (D_(max)) is 7+/−1 mm. In someembodiments, the dose rate is 1500+/−10% MU/min at 450 mm Source to AxisDistance (SAD); 1 MU=1 cGy at SAD=450 mm, 25 mm field size at D_(max).In some embodiments, the LINAC subsystem includes a custom LINAC controlboard, automatic frequency control board (AFC), dosimeter and dosimeterboard for incorporation into a self-shielded treatment system inaccordance with aspects of the present invention.

F. Imaging & Monitoring Subsystems

In order to meet certain radiosurgical precision requirements, thetreatment system can include an imaging and monitoring subsystem thatprovides a means of tracking the position of the tumor with respect tothe system isocenter. In some embodiments, for tracking purposes, theself-shielded capsule is equipped with a kV tube with an X-ray supply,along with a kV imaging detector. Prior to activating the radiationbeam, the imaging and monitoring subsystem takes images of the patienthead and verifies that the tumor is in position (e.g., located at theisocenter). In case of a position discrepancy, the patient tableautomatically moves to compensate for the position discrepancy bringingthe anatomical target into the system isocenter.

In some embodiments, in order to monitor patient position (andinferentially with respect to the LINAC, the imaging and monitoringsubsystem includes an imaging radiation source fixed in a first shieldcomponent and a radiation detector affixed in a second shield componentopposite the radiation source. In the embodiment described herein, theimaging radiation source is a kilo-voltage X-ray source and the imagingradiation detector is an amorphous silicon flat panel detector, althoughit is appreciated that any suitable imaging radiation source anddetector could be used in other embodiments. During treatment, thesubsystem obtains images of the patient anatomy episodically, determinespatient movement, if any, and directs the patient table subsystem toadjust the patient position to position the tumor at the systemisocenter as needed.

In one aspect, the imaging and monitoring subsystem is configured with asequential view tracking methodology. The system performs imaging, inwhich at least two images are obtained sequentially from the imaging andmonitoring subsystem to determine a position of the target. In theembodiments described herein, the kV tube and detector are used toacquire live patient image. In contrast, conventional systems, such asCyberKnife system or Brainlab system, use two sets of imaging devicesfor stereo image tracking. Stereo image tracking combines trackingresults from each imaging system to form six degree of freedom results.To have a quick and accurate solution for patient alignment andtracking, the embodiments described herein utilize a moveable imagingsubsystem to obtain sequential views from different perspectives towardthe patients head. For example, the imaging radiation source can be usedwhile the first shield component is at a first position to obtain afirst image, and then the first shield component can be rotated to movethe imaging device to a second position to obtain a second image fromanother perspective, the first and second images being used to determinealignment of the target with the isocenter. The system can be used inboth initial patient alignment and tracking during delivery. Whileembodiments described herein include a single diagnostic radiationsource, it is appreciated that in some embodiments, multiple sources atdifferent locations on the first shield components could be used.

An exemplary imaging method utilizing sequential view trackingmethodology can include the following steps:

-   -   1) Obtain first image at a first location of the diagnostic        imaging system and correlate the X-ray image with digitally        reconstructed radiograph (DRR) image to get accurate 2D        translation (TX1 and TY1).    -   2) Move the diagnostic imaging system (typically by movement of        a gantry or shield assembly on which the system is mounted) to        at least a second location (can be a single axis motion, or        combination of two axes), and correlate again to get second        accurate 2D translation (TX2 and TY2).    -   3) Based on displacement matrix (i.e., rotation) between those        two locations, combine two results (TX1/TY1, TX2/TY2) to        calculate depth result of (TZ2).    -   4) Combine depth results (TZ2) with current location result        (TX2/TY2) to form a 3D translation result (TX2/TY2/TZ2).    -   5) If any table motion happened between those two imaging        locations, the displacement matrix (in Step 3) can also include        table translation.    -   6) To get an accurate and robust TZ2 result, several approaches        may be used:        -   a. A minimal rotation angle reduces noise. (e.g. 20 degrees            or greater, typically an angle between 40 and 70 degree,            preferably about 60 degrees).        -   b. A heuristics approach can be used to combine more than            two images. For example, the sequential view results can be            generated from the last image with all historical (previous,            previous −1, previous −2, . . . ) images. Only the last few            are used to avoid potential patient motion, and any outliers            are removed to find the average results.        -   c. An iterative approach can also be used between (3) and            (4).    -   7) In addition to 3D translation result, 3D rotations can be        calculated separately after initial position is close to the        aligned position using coordinate descent or related        optimization approach        -   a. Search RotationX to find best match within a range (for            example, −5 to +5), while fixing RotationY and RotationZ.        -   b. Keep optimized RotationX, then search for optimized            RotationY and RotationZ until new best values are found.    -   8) After initial rotations are found, optimization can be done,        and steps 1 to 4 are optionally repeated for patient alignment.

G. MV Radiation Beam Monitor Subsystem

In another aspect, the system monitors the MV (therapeutic) radiationbeam during treatment with a MV radiation beam monitor subsystem. Thepurpose is not to determine the position of the patient (as with the kVbeam), but rather to verify and quantify the radiation intensity thatpasses through the patient. When captured after having passed through apatient (and knowing how much radiation was output by the LINAC), theresidual radiation can be correlated with how much radiation the patientabsorbed by comparing to the amount of radiation expected to be passedthrough the patient.

In some embodiments, the output of the MV radiation beam is measured byuse of a MV radiation beam monitor subsystem that includes ascintillating membrane and one or more cameras that detect light fromthe scintillating membrane and output a corresponding signal. Theresultant digitized signal is then processed through video signalprocessing electronics and fed into a system computing unit. The systemcomputing unit can then determine the dose data, beam profile data andthe beam positioning data. One potential advantage of this embodiment ishigher spatial resolution of the data since a high-resolution camera canbe employed. A second advantage of this embodiment is simplicity andcost.

In some embodiments, the MV radiation beam monitor subsystem includes aremovable MV radiation beam monitor unit, which is to be replaced beforeeach treatment to ensure the MV radiation beam monitor performs properlyand does not degrade with re-use. In some embodiments, the unit includesa removable MV detector camera with scintillating sheet. Typically, thescintillating sheet is made of phosphor Gd₂O₂S:Tb (GOS) on a silicone(PDMS) matrix and cast into a sheet. For every beam delivered,corresponding images are stored on the computer. The camera may be useda single time and replaced because the CCD camera degrades with MVradiation; a new factory-calibrated camera ensures accurate reading eachtime. The removable MV radiation beam monitor unit includes one or morecoupling and/or alignment features to ensure consistently accuratespatial placement. The alignment features can include positive stops andpositive locking mechanisms, for example, including magnets, latches,pegs, mortices or any suitable means. In some embodiments, the shieldcomponent in which the removable MV radiation beam unit is attachedincludes a contoured region that facilitates a desired placement of theunit or orientation, for example, the scintillating sheet beingsubstantially perpendicular to the MV radiation beam. The contouredregion is dimensioned to receive the removable unit and can include thepositive stops and positive locking mechanisms therein to facilitatesecure attachment of the removable MV radiation beam unit at a desiredposition, alignment and orientation. In addition to CCD, the imagingdevice include CMOS cameras, or any other digital imaging device.

A substantial deviation from expected dose to the measured dose willindicate an anomaly and the system will be shut down via the integratedcontrol subsystem. This subsystem can include various inter-connectcables and other ancillary devices. Some of the ancillary devicesinclude cameras and an intercom for the user to monitor and interactwith the patient during the treatment. The system provides real timemonitoring of the dose prescribed to the patient for each LINACposition. This monitoring feedback feature ensures that the treatmentplanning is delivered as prescribed and, in one embodiment isimplemented with an MV imager that undergoes a change in response toabsorbed radiation, and may be replaced with a new, factory-calibratedunit.

In some embodiments, the MV radiation beam monitor subsystem includes aremovable single-use MV detector with silicon diode-based MV detector.In some embodiments, the single-use MV detector includes a scintillatorand one or more photodiodes. Such a detector allows use of varioustechniques for in-situ radiation intensity measurement to quantify thequality of the treatment and provides data on in-situ positioning of theradiation beam, intensity distribution within the beam without thepatient in the beam path, and residual beam with the patient in the beampath. The dose delivered for each site can be determined using thismeasurement for verification, with or without the patient in the beampath. The measured residual dose can be determined from a therapeuticbeam detector unit and measured at multiple points. The theoreticalvalue of the residual dose that is determined by the treatment planningsystem can be compared with a measured residual dose value using thistechnique for validation of the treatment and/or to assess treatmentdelivery quality. Validation or quality determinations can be recordedand used to adjust subsequent therapy delivery. In some embodiments, theoutput of the diode array is amplified, digitized and fed to a smartcontroller where the data is sorted and scaled and sent to an onboardsystem computer. The system computer with additional processing can beused to determine dose delivered data, the beam profile data, and beampositioning data. The LINAC that provides the high energy X-Rays, ismodulated with a very small duty cycle (e.g. 500:1 duty cycle).Typically, the beam is only on for less than 1/300^(th) of the time(e.g. 1/500^(th) of the time), the rest of the time the beam is off;however, the time constant of the scintillator can be almost 3 orders ofmagnitude slower. The signal acquisition is synchronized with the ontime of the radiation pulse to maximize the amount of signal to be read.This technique helps with the signal to noise ratio for low-levelsignals. In order to characterize the therapeutic radiation beamquality, spatial position and intensity measurements of the beam can becarried out. These values can be used to characterize the beam qualityduring the QA period of the system; can be used during the treatment toprovide beam position and intensity distribution data, and can be usedwith a secondary dose measurement to validate actual dose delivered isdesired and to quantify the quality of the treatment. For example, aresidual dose measurement of the beam after passing through the patientcan be used to compare with a calculated residual dose to validate thequality of the treatment. By analyzing the residual beam intensitydistribution along with the CT data, one may be able to determine thepositional accuracy of the beam with respect to the tumor during thetreatment.

In one aspect, the MV radiation beam monitor subsystem includes ascintillator positioned incident to the high energy X-ray radiation suchthat the radiation excites the scintillator atoms that in turn produceemission of photons in the visible range. The visible light intensity isproportional to the radiation intensity. In some embodiments, a seriesof photodiodes are used to convert the visible light to electricalsignals as an input to the system computer. The scintillator convers theradiation to visible light in the range of the photodiode's detectionrange. The photodiode array can be placed immediately after thescintillator to maximize the signal level and improve the signal tonoise ratio. A number of diodes sufficient to cover the beam diametershould be used in order to provide a beam intensity profile measurement.There are various different photodiode array configurations that couldbe used. In some embodiments, the photodiode array utilizes 16 elementdiodes per chip and a sufficient number of chips to cover the entirebeam using the largest collimator aperture. The electrical signal fromthe diode arrays are then amplified and digitized and fed to a computer.The computer software digitally processes the signal and produces dosemeasurement for validation during the treatment, as well as producingthe beam intensity profile, and the XY position data. The XY positionaldata may be used to validate the accuracy of the beam's position on thetumor and to report possible errors.

Other light detection methods such a CMOS or CCD camera can also beused. In some embodiments utilizing CCD cameras, due to the small sizeof the camera's active area, such configurations typically use multipleoptical components to project the image to the camera. The opticstypically require that the CCD cameras be placed some distance away fromthe scintillator to allow room for focusing. The signal intensityreceived by the CCD camera is calibrated to a known radiation intensity,thereby compensating for any loss of light occurring in the interposeddistance between scintillator and CCD.

II. DETAILED EXAMPLES

FIG. 1 illustrates an overview of an exemplary self-shielded treatmentsystem, which includes the mechanical subsystem, the largest piece ofhardware in the system. The system includes a shield that includes twomovable shield components, oblique shield 101 and axial shield 105oblique shield 101 rotating on oblique axis 130 and axial shield 105rotating on axial axis 135. Upon rotation of axial shield 105, bothaxial shield 105 and oblique shield 101 are rotated about axis 135,while oblique shield 101 is independently rotatable about an obliqueaxis 130 that is transverse to the axial axis 135. Patient 150 is lyingwithin the apparatus on a patient table (not shown) substantiallyaligned along axial axis 135 with target at isocenter 136 located atintersection of axial axis 135 and oblique axis 130. Mounted on theinner surface of oblique shield 101 is LINAC 110 that produces MVradiation therapy beam 145 that passes through patient 150 and receivedby MV radiation detector 115 also mounted upon the inner surface ofoblique shield 101. Mounted upon the internal surface of axial shield105 is KV radiation emitter 120, which is used for real-time X-rayimage-based position sensing by passing its beam 140 through patient 150to kV radiation detector 125 mounted on the internal surface of obliqueshield 101. It is noted that the shield components depicted are of solidconstruction and hatch lines have been omitted merely for clarity.

FIG. 2A shows the mechanical subsystem of the treatment system ingreater detail as viewed from the side. In this embodiment, thesubsystem is housed in a floor pit, although it is appreciated that thesubsystem could also rest on a floor surface without a pit assumingsufficient overhead clearance. The axial axis 211 turns via the axialbearing assembly (not visible as it is obscured by base ring) withmultichannel electrical and electronic supplies rotationally commuted byaxial slip rings 212. Axial shield 205 turns on axial axis 211 aroundthe torso of the patient within. Oblique axis 216 turns on obliquebearing assembly 217 with multichannel electrical and electronicsupplies rotationally commuted by oblique slip rings 218. Oblique shield204 is covered by and enclosed with system electronics by obliquesupport bracket 215. Shell 265, which rotates on shell bearing 266,covers and shields the entry portal from above the patient table base260 when the system is in the closed, shielded configuration. Portal isthe entryway into the interior of the device that encloses the upper ⅔of the patient table when door 275 and shell 265 are in the closed andshielded configuration.

In this embodiment, the treatment system sits within a formed concretepit 255 approximately two feet deep. The pit serves as additionalradiation shielding for the lower portion of the device, andadvantageously places the patient bed (not shown here) at a comfortableheight for seating and bringing patients in and out of the device to thefloor level. The pit also reduces the ceiling height required for theapparatus in the room, and makes the apparatus more aestheticallyappealing by appearing smaller. Portions of the pit not occupied by theapparatus itself can be covered by flooring 251 that meets the normalfloor level 250 of the apparatus. The entire mechanical apparatus isheld together chiefly by a strong central base ring 257 which isanchored to the concrete at the bottom of pit 255 with ring base 256 andbalances the weight of oblique shield 204 and axial shield 205 and othermassive components of the system. It is appreciated that ring base 256can be an integral portion of base ring 257, as shown here, or can aseparate component attached thereto. A deeper extension of the pit 254accommodates the vertical travel needs of door 270 at its fully openedposition.

In this embodiment, the treatment system includes proximity detectors259 disposed near the base on each side to detect proximity of a personso as to effect an automatic shut-off of radiation and motion uponunauthorized entry of a person into an immediately surrounding zone soas to prevent unintended exposures to radiation or contact to movingsystem parts during treatment. In some embodiments, the proximitydetector has a detection range of at least 180 degrees, typically up to270 degrees such that one proximity detector on each side of thetreatment system effectively covers a zone extending around the entiresystem. Alternatively, a single proximity detected with a 360 degreerange could be positioned above the entire system. The area covered bythe proximity detectors can be marked by a boundary. Such aconfiguration can allow the area outside the boundary to be anuncontrolled area since there is little risk of unintended exposuresince the system will shut off if the boundary is crossed.

FIG. 2B shows a view of the mechanical subsystem as viewed from thefront. Door 275 is vertically lowered to an open position therebyrevealing portal opening 271. Through portal opening 271, collimator 280and patient table 290 are visible within the interior. In thisembodiment, door 275 is opened by lowering it into pit extension 254,using the door mechanism including door actuator 276 (e.g. a hydraulicjack) and using the space provided by this yet deeper portion 254 of pitbase 255. Such a configuration is advantageous as it reduces theclearance required around the portal opening for the door and associatedmovement mechanisms. It is appreciated that in various otherembodiments, the door can be lowered from above or could be translatedor rotated into position from any direction.

In this embodiment, the entire mechanical superstructure is linkedtogether and supported by base ring 257, which substantially balancesthe massive loads of heavy shielding and other equipment on either side.Axial bracket 258 covers the axial shield and serves to cover essentialelectronics in a manner analogous to the oblique bracket on oppositeside of the machine (not shown). Note that shell 265 is in the openposition, where it has rotated about shell bearing 266 to underliepatient table base below patient table 290, leaving patient table 290exposed from above. This position allows the patient table to rolloutward to its full extent, enabling patients to be loaded and unloadedfrom the apparatus. Upon loading, patient table 290 rolls toward thecollimator, shell 265 rotates about shell bearing 266 until the shellcovers patient table 290, and door 275 on door actuator 276 raises intothe closed and shielded position.

FIG. 3 schematically illustrates the axes of movement of an exemplarymechanical subsystem and their relationship to one another in asimplified paradigm in accordance with aspects of the invention. Axialaxis 301, in the system, controls movement of a first shield component(e.g. axial shield). Oblique axis 305, in the system, controlsindependent movement of a second shield component (e.g. oblique shield).The shield components have been omitted to better illustrate their rangeof movement provided by their respective axes. In this embodiment, LINAC310 is coupled to the oblique axis 301 via the associated obliqueshield, such that LINAC 310 is capable of irradiating targets withinpotential treatment volume 315. As can be seen the potential treatmentvolume 315 is a substantially spherical shape about the isocenter (notshown). It is appreciated that, in this embodiment, oblique axis 305 maymove independently of axial axis 301, but movement of axial axis 301necessarily results in movement of oblique axis 305 about axial axis301. Although this configuration provides considerable range of movementof the treatment beam to the target, there is a portion of the treatmentvolume 315 located distally of axis 301 that the LINAC cannot reach.Optionally, this portion can be effectively reduced by use of a patienttable that can move the target along one or more axes to the accessibleportion of the treatment sphere. An example of such a patient table isdescribed in further detail below. In some embodiments, each of theaxial shield and the oblique shield are rotatable 360 degrees abouttheir respective axes of rotation. It is appreciated however, that thisrange of rotation of each shield component is not required to maintainfull range of movement of the treatment beam, for example, one of theshield components can be rotatable by only 180 degrees so long as theother shield component is rotatable by 360 degrees.

FIG. 4 shows an example patient table and its axes of motion inaccordance with aspects of the invention. Patient table 400 supports andpositions the patient for correct MV radiation beam aim duringtreatment. Patient table 400 has two y-axes 431 of motion, a pitchmotion around the x axis 433, and a yaw motion around the z axis 432.Lower cart 405 moves along the y-axis 431 of table base 410, as doesupper cart 412. Pitch plate 415 rotates around the pitch axis, which isparallel to x-axis 433, in a pitch fashion by raising or lowering thehead end of the patient bed 420 along z-axis 432. The patient bed 420rotates about the yaw axis, which is perpendicular to the x-axis, in ayaw fashion by moving the head of the patient bed left or right alongx-axis 433. The patient bed has headrest portion 425 that includesfacets for attaching a radiosurgical stabilizing face mask. Optionally,the headrest 425 can include an additional pitch joint that can beautomatically moved so as to move the target so as to increase theaccessible portion of the treatment sphere. Typically, the additionalpitch joint is configured to allow headrest 425 to pitch between a 30degree incline and decline, so as to further reduce the inaccessibleportion of the treatment sphere. The associated movement of each tablecomponent are described further below and depicted in FIG. 5

FIG. 5 shows the example patient table of FIG. 4 with the associatedaxes of motion along with a simplified model of those axes. Table base505 supports the x-axis translation movement of the table. Lower cart510 rolls in a first x-axis translational motion. Upon lower cart 510rolls upper cart 515 for a second x-axis translational motion. Pitchplate (pitch rotation) 520 is moved in a pitch motion, being affixed atthe portion that accommodates the patient's buttocks, and free to movein pitch fashion at the end that accommodates the patient's head. Thepatient bed 525 also rotates in a yaw fashion. Headrest 526 pitchesalong a pitch axis. This configuration of movable components of thepatient table facilitate positioning of the patient through the entryportal and positioning of the target within the patient (e.g. patient'shead) within the treatment space within the movable shields. While aparticular configuration of table components and associated joints aredepicted here, it is appreciated that alternate configurations of jointscould be utilized to provide the same or similar range of movement inaccordance with the invention.

FIG. 6 illustrates an example main integrated control system thatmonitors and controls all hardware and software systems of a treatmentsystem in accordance with aspects of the present invention. Patienttable 600 serves to position patient and immobilize the patient's headin the correct position so that the tumor is isocentric, and isnetworked to the control and safety subsystem 620. Imaging andmonitoring subsystem 605 obtains diagnostic images (e.g. obtains kVX-ray images for patient alignment and tracking) and performs monitoringand/or verification of the treatment radiation beam (e.g. measures MVradiation exiting the patient). This subsystem can also provide videoand audio communication with the patient. Subsystem 605 can be networkedto control and safety subsystem 620. Mechanical subsystem 610 providesradiation shielding and controls movement and position of the LINAC andcan be networked to control and safety subsystem 620. LINAC subsystem615 creates the MV radiation beam and delivers it to the patient, withinternal output measurement provided in the dual ion chamber, and can benetworked to control and safety subsystem 620. Control panel 625provides manual controls for LINAC on/off function, speaker andmicrophone for patient communication and other functions, and can benetworked to control and safety subsystem 620. Operator PC 630 runs thetreatment delivery subsystem and can be networked to control and safetysubsystem 620. Control PC 635 controls system hardware and is networkedto control and safety subsystem 620. Planning and database PC 640 runsthe treatment planning subsystem and associated database and can benetworked to control and safety subsystem 620. Pendant PC 645 runspendant application and is networked to control and safety subsystem620. It is appreciated that the above systems can be networked to thecontrol and safety subsystem by hardwired connections or through awireless network.

FIG. 7 is a schematic illustrating the balancing of the weightdistribution of the axial shield and oblique shield of the radiationshield. Axial shield 702 rotates about axis a₂ and is movably interfacedwith oblique shield 701 such that rotation of the axial shield 701 alsorotates the oblique shield about axis a₂. Given the differing geometriesand distribution of mass of the axial and oblique shields, the rotationof the radiation shield would typically require relatively large,oversized motors in order to accommodate the substantial variations inreaction forces during a single rotation of the shield. To avoid thesevariations, one or more counterweights can be mounted on the respectiveshield components in order to distribute weight more uniformly about theaxis about which each rotates. In this embodiment, the oblique shieldcomponent is balanced around the oblique axis about which it rotates andthe axial shield and oblique shield assembly are balanced around theaxial axis about which the assembly rotates. In turn, the axial andoblique shields can be counterbalanced about a common support, base ring704 that extends around the radiation shield assembly and includes alower base portion 705. FIG. 7 shows the center of gravity CG₁ of themass m₁ of oblique shield 701 balanced around the oblique axis, which isoffset from the axial axis a₁ by distance_(d1). The center of gravityCG₂ of the mass m₂ of axial shield 702 is offset from the axial axis a₂by a distance of dz. Therefore, to balance the shield assembly about theaxial axis a₂, a counterweight 703 of m₃ is mounted to the axial shield702 at a distance of d₃ from the axial axis, according to the equation:m₃d₃−m₂d₂=m₁d₁. While only one counterweight is shown in this example,it is appreciated that such balancing can include additionalcounterweights mounted on the various shield components as needed. Suchan approach of counterbalancing the shield components and shieldassembly about their respective axes of rotation reduces the motorrequirements needed to rotate the shield components as described herein,thereby reducing the overall size and footprint of the device as well asreducing cost and complexity of the mechanical drive system.

As shown, the axial and oblique shields counterbalance each other aboutthe common support ring. Typically, the central base support ring isdisposed vertically substantially between the centers of mass, althoughin some embodiments, the central base support ring can be coincidentwith the centers of mass or extend a distance beyond. In one aspect, theangled interface between the axial shield and oblique shield (e.g., 45degrees) allows the centers of mass to be relatively near each other,which allows the slew drive ring that rotates the shield assembly driveby one or more linear motors to be centrally located on support ring704.

FIG. 8 illustrates an embodiment that includes a MV therapeuticradiation monitoring or verification subsystem in which the MVtherapeutic radiation having passed through a patient onto ascintillator is captured by a photodiode array with the resulting signalprocessed and registered in the system computer. In this embodiment,LINAC 805 emits MV therapy radiation beam 815, which passes throughcollimator 810 and then through the targeted portion of patient 820. Theremaining radiation beam then strikes scintillator 825, which glows withvisible light at an intensity proportional to the intensity of radiationbeam 815. The glowing of scintillator 825 is transduced by photodiodearray 830 into electronic signals 831 from those component photodiodes.The signals are passed collectively or in segregated form throughamplifier 835, analog-to-digital converter 840, and then to signalprocessing computers 845. The resultant processed signal is then sent tosystem computing unit 850. This process occurs continuously during thetreatment session, thereby verifying the total amount of radiationreceived over the session. In some embodiments, a beam stop (not shown)is placed directly in the MV radiation beam's path immediately after thescintillating sheet or diodes.

FIG. 9 illustrates another embodiment with an alternate means forverifying the amount of radiation that has passed through the patient bycapturing the fluorescence from a scintillating sheet using a CCDcamera. In this embodiment, LINAC 905 outputs MV therapy radiation beam915, which passes through revolving collimator 910 and to the targetedregion of the head of patient 920. After passing through patient 920, MVradiation beam 915 strikes scintillator 930. In response to being struckby MV radiation 915, scintillator 930 produces visible fluorescent light925 that is proportional to the intensity of the radiation beam.Fluorescence 925 is captured by CCD camera 935, which outputs a signalwith image information. The image information is then passed in realtime to video data acquisition electronics 940, video signal processingelectronics 945, and ultimately passed to system computing unit 950which documents and certifies that the amount of radiation treatmentthat the patient has received. Because the fluorescence captured by CCDcamera 935 reflects radiation that has already passed through thepatient, the system computing unit 950 can receive a more accurateassessment of the radiation received by the patient than in systems inwhich the radiation intensity measurement is done prior to passing thebeam through patient 920. It is appreciated that this approach can beused in place of or as a supplement to an intensity measurementperformed prior to passing the beam through the patient. In variousembodiments, this process occurs continuously during the treatmentsession, thereby verifying the total amount of radiation received overthe session. In some embodiments, beam stop 931, typically a piece ofthick shielding, is placed directly in the MV radiation beam's pathimmediately after the scintillating sheet or diodes. Beam stop 931ensures that the high-intensity radiation in that location is nottransmitted externally of the shielded apparatus.

FIG. 10 illustrates a removable and replaceable scintillator/cameracombination for use with treatment system in accordance with aspects ofthe invention. Preferably, this is a consumable piece of hardwarecontaining the scintillating sheet and CCD camera that is removed andreplaced between each patient use, insuring that a freshly calibratedCCD camera is used every time for the most accurate possible readingsdelivered to the treatment verification system and associated databaserecord. Removable housing 1020 has affixed scintillating sheet 1010 andaffixed CCD camera 1015, and thus may be removed as a unit and replaced.Since radiation degrades the CCD camera over time, more accurate MVdetection can be achieved by replacing the unit between radiosurgicaltreatments. Housing 1020 may be positively affixed to mounting base 1035by one or more removable coupling features. In some embodiments, the oneor more coupling features are configured to ensure a proper alignmentand/or orientation of the unit within the interior of the shield so asto provide consistent, reliable monitoring and verification of thetherapy beam. The one or more coupling features can include any suitablemeans of coupling, which may include: pegs and mortices, latches, and asshown in FIG. 10, magnets 1030 that are attracted to precisely placedferrous metal tabs 1025. Mounting base 1035 can be affixed to theshielded wall 1040 of the mechanical subsystem within the MV radiationbeam's path. Florescent visible light captured by CCD camera 1015 isproportional to the high-energy (MV) x-ray beam intensity. Since a newfactory-calibrated CCD camera is in each removable housing 1020 and usedwith each patient, the highest treatment verification standards aremaintained.

III. IMAGING AND TRACKING METHODOLOGY

FIG. 11 illustrates an exemplary tracking methodology framework. In someembodiments, the tracking method includes enhancement 1105 of kV and DRRimages in parallel. Enhancement can include use of noise filters,contrast and brightness, etc. Next, pyramid resampling of image 1110 canbe used to enable efficiency of the process by permitting the system towork on lower resolution images first to remove noise and local minima,but can return to full resolution in the final step. Next, the methodcan transform the images 1115, which can include rotation, translation,and scaling. Then, the images can be segmented into regions 1120 on aregular grid. Segmenting into regions serves to exclude unwanted partsof the image such as moving parts of the skull (e.g. jaw) that canreduce accuracy over overall pattern matching. Next the method canconduct similarity measurement and search assessment 1125. Similaritycan be assessed using difference of gradient and can further utilize agradient descent or coordinate descent optimization method withsimilarity curve fitting. Lastly, the method can include verification1130, which can be based upon convergence.

FIG. 12 is a process schematic for optimization of tracking. In step1205, kV images are acquired from the imaging and monitoring subsystem.After the raw images are acquired, offset and gain calibration areperformed to get uniform intensity and remove detector artifacts, suchas bad pixels. In step 1, real-time digitally reconstructed radiograph(DRR) images are generated based on system geometry and target location.After 2D DRR images are generated, some image enhancement steps, such ascontrast enhancement, can be used to emphasize certain features. Thisstep can require extensive calculation, and can be accelerated by GPU.In step 1215, image enhancement approaches are used for in-planetransformation estimation. In-plane transformation includes two in-planetranslations, and one in-plane rotation. In step 1220, algorithm usescoordinate descent approach to find the optimized solution of in-planeparameters. For example, algorithm can find in-plane rotation (RZ)first, then find TX and TY, or find TY first and then TX. The finaloptimization transformation, including RZ, TX and TY are found. In step1225, image enhancement approaches are used before out-planetransformation estimation. Out-plane transformation include twoout-plane rotations, and one out-plane translation. Due to weak signalof depth features, out-plane enhancement may be different than in-planeenhancement as described in step 1215. In step 1230, the algorithm usescoordinate descent approach to find out-plane rotations RX and RY.Either search RX first or search RY first. In step 1240, the last stepof algorithm is to optimize out-plane translation (e.g., depth).

FIG. 13 schematically illustrates movement of the mechanical subsystemto obtain kV images of the identified target in accordance with thesequential viewing methodology. In this concept view of axial rotationfrom entry, the axial rotation path 1305 is represented by a circle.Target is in the center of that circle 1305 defined by rotationalmovement of the axial shield. In step 1310, a first kV image is obtainedfrom position A, where the kV X-ray tubes are located at the top and thekV detector is located at the bottom. In step 1315, the axial shield isrotated to position B, where kV X-ray tubes are located at the right andthe kV detector is located on the left. In step 1320, the sequentialview algorithm uses kV images acquired from position A and B tocalculate target offset. Patient table is then moved to compensate forthe offset. In step 1325, another kV image is obtained at position C(same as position B except the patient table has been moved). In step1326, the axial shield is rotated back to position D (same as position Aexcept table has been moved). In step 1330, another kV image is obtainedat position D. In step 1335, the sequential view algorithm uses kVimages acquired from position C and D to calculate the target offset.The patient table is moved to compensate the offset. In step 1340, ifthe last calculated offset from step 1335 is less than a pre-definedthreshold (for example, 0.5 mm), the initial alignment is finished sincethe target is aligned at the isocenter; otherwise, the tracking methodcan repeat steps from step 1310 until the target is aligned.

FIG. 14 schematically illustrates imaging at first and second positionsin sequential view imaging in accordance with some embodiments. InPosition 1, the diagnostic radiation beam emitter 1420 directs adiagnostic imaging beam 1440 through the target, while a diagnostic beamdetector unit 1425 measured the residual beam passed through the target.In Position 2, the diagnostic radiation beam emitter 1420 and thedetector unit 1425 have been revolved around an axis extending throughthe isocenter to Position 2, at which a second image is obtained.Typically, the second position is at least 20 degrees from the firstposition. The first and second images can be utilized, as describedpreviously, to determine a diagnostic result to facilitate delivery oftherapy.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modifications, adaptations, andchanges may be employed. Hence, the scope of the present inventionshould be limited solely by the appending claims.

In the foregoing specification, the invention is described withreference to specific embodiments thereof, but those skilled in the artwill recognize that the invention is not limited thereto. Variousfeatures, embodiments and aspects of the above-described invention canbe used individually or jointly. Further, the invention can be utilizedin any number of environments and applications beyond those describedherein without departing from the broader spirit and scope of thespecification. The specification and drawings are, accordingly, to beregarded as illustrative rather than restrictive. It will be recognizedthat the terms “comprising,” “including,” and “having,” as used herein,are specifically intended to be read as open-ended terms of art.

1.-39. (canceled)
 40. A removable therapeutic radiation beam detector unit comprising: a scintillating detector; one or more photosensors configured and arranged at a substantially fixed position and alignment relative the scintillating detector for measurement of light emitted from the scintillating detector; a connector coupled to the one or more photosensors to facilitate external control of the one or more photosensors and transmission of an output from the photosensors to an external control device; and one or more releasable coupling features to facilitate secure mounting of the unit within a radiation treatment system to facilitate monitoring or validation of a therapeutic radiation beam with the unit.
 41. The removable therapeutic radiation beam detector unit of claim 40, wherein the scintillating detector is a scintillating membrane and the one or more photosensors comprise one or more digital imaging detectors.
 42. The removable therapeutic radiation beam detector unit of claim 40, wherein the scintillating detector is a scintillating membrane and the one or more photosensors comprises one or more photodiodes.
 43. The removable therapeutic radiation beam detector unit of claim 40, wherein the one or more coupling features includes one or more of: a magnet, a latch, a peg, a mortice, snap, hook, loop, slots, screws, clasps, or any combination thereof.
 44. The removable therapeutic radiation beam detector unit of claim 40, wherein the one or more coupling features are configured to releasably secure the unit in a particular alignment and/or orientation within the radiation treatment system so that the therapeutic radiation beam is incident on a radiation receiving surface of the scintillating detector. 45.-71. (canceled)
 72. The removable therapeutic radiation beam detector unit of claim 40, wherein the scintillating device comprises a scintillating sheet.
 73. The removable therapeutic radiation beam detector unit of claim 40, further comprising: a housing to which the scintillating detector and the one or more photosensors are affixed and having the one or more releasable coupling features thereon such that the housing can be mounted and removed as a unit.
 74. The removable therapeutic radiation beam detector unit of claim 73, wherein the housing is shaped to correspond to a contoured region of the mount to receive the housing in a particular alignment and/or orientation within the radiation treatment system.
 75. The removable therapeutic radiation beam detector unit of claim 40, wherein the one or more releasable coupling features are configured to positively secure to a mounting base within the radiation treatment system.
 76. The removable therapeutic radiation beam detector unit of claim 40, wherein the one more releasable coupling features comprise a plurality of magnetic or ferrous metal tabs positioned for magnetic coupling with corresponding magnetic or ferrous metal tabs of a mount within the radiation treatment system.
 77. The removable therapeutic radiation beam detector unit of claim 40, further comprising: a mounting base configured for coupling with the one or more coupling features of the detector unit, wherein the mounting base is configured for being affixed inside the radiation treatment system.
 78. The removable therapeutic radiation beam detector unit of claim 77, wherein the mounting base is shaped or contoured to receive a housing of the detector unit.
 79. The removable therapeutic radiation beam detector unit of claim 40, wherein the one or more photosensors are positioned within the detector unit adjacent the scintillating device so that florescent light captured by the one or more photosensors are proportional to an intensity of a treatment beam of the radiation system, wherein the detector unit is mounted within the radiation treatment system.
 80. The removable therapeutic radiation beam detector unit of claim 40, further comprising: an amplifier that receives signals from the one or more photosensors.
 81. The removable therapeutic radiation beam detector unit of claim 40, further comprising: an analog-to-digital converter that receives the signals from the amplifier.
 82. A radiation treatment system comprising: a radiation treatment source configured to emit a radiation treatment beam; a control unit for positioning the radiation treatment source; and a removable therapeutic radiation beam detector unit as in claim 40, wherein the detector unit is communicatively coupled with the control unit for image-based monitoring, verification and/or positioning of the radiation treatment beam.
 83. The radiation treatment system of claim 82 wherein the control unit is configured to: store calibration data of the detector unit; store a treatment plan; calculate a radiation measurement from an output of the detector unit and the calibration data; and deliver the treatment plan using the stored treatment plan and the calculated radiation measurement.
 84. The radiation treatment system of claim 83, wherein the detector unit is factory calibrated or is calibrated within the radiation treatment system to a known radiation intensity.
 85. A therapeutic radiation beam detector unit comprising: a radiation measurement means for measuring radiation of a treatment beam; and a removable coupling means for securing the radiation measurement means within a radiation treatment system to facilitate monitoring and/or verification of the treatment beam.
 86. A therapeutic radiation treatment system comprising: a radiation means for emitting a treatment beam; a control means for controlling trajectory of the treatment beam; and a removable detector unit as in claim 85 placed along a trajectory of the treatment beam.
 87. The therapeutic radiation treatment system of claim 86 further comprising: a means for storage of calibration data of the radiation measurement means; a means for storage of a treatment plan; a means for calculating a radiation measurement from an output of the radiation measurement means and the calibration data; and a means for delivering the treatment plan using the stored treatment plan and the calculated radiation measurement.
 88. The therapeutic radiation treatment system of claim 87, further comprising: a means for providing real-time feedback to the radiation source control means from the removable radiation measurement means.
 89. The therapeutic radiation treatment system of claim 88, wherein the system is configured such that the feedback comprises: shutting down treatment in response to determining a substantial deviation from an expected dose and/or adjusting subsequent treatment delivery based on an output from the detection unit. 